1. Field of the Invention
The present invention relates to a method and apparatus for determining relative humidity in the air passing through the evaporator of an air conditioner.
2. Description of the Prior Art
A well designed complete air conditioning system is capable of achieving the following goals:
1. Temperature control; PA1 2. Humidity control; PA1 3. Air movement and circulation; and PA1 4. Air filtering, cleaning and purification.
In most residential air conditioning installations good engineering of the system including the compressor, heat exchangers, fans expansion devices and other controls result in accurate temperature control to a desired set point. Humidity control generally is achieved by movement of the inside air past the evaporator coil to reduce the temperature of the moisture laden air to at least the dew point temperature in order for moisture to condense out the air. Humidity controls for the operator to set, or, for that matter, automatic control of dehumidification is norma not provided in such systems as accurate humidity sensors are quite expensive.
With the development of air conditioning systems making use of variable speed motors for driving the compressor and fans it has become possible for an air conditioning system to be operated in different modes of operation depending upon the relative humidity level in the air being cooled. In order to make use of such capability it is necessary for the microprocessor controller of such a system to have an input from a humidity measuring device. As pointed out above, such devices are quite expensive and do not lend themselves to being economically incorporated into a small room or residential air conditioning system.